Rare earth-based oxide ceramics are generally prepared by molding methods including mold pressing, rubber pressing (or isostatic pressing), slip casting, and doctor blade methods. There is furnished rare earth-based oxide powder. Ceramic compacts are shaped from the powder by any of these molding methods. The compacts are subjected to firing, sintering and working steps until they are finished into products of the predetermined size.
However, where it is desired to prepare rare earth-based oxide ceramic thin plates, especially thin plates having a thickness of up to 5 mm and a volume of at least 50 cm3, by the molding method, cracks occur during the molding step, which makes it difficult to obtain molded compacts. One common solution to this problem involves molding compacts having a greater thickness so as to ensure higher yields of compact formation, firing and sintering the compacts, and grinding or otherwise machining the compacts into thin plates having a thickness of up to 5 mm.
This method, however, is disadvantageous in that as the final thin plate becomes thinner in thickness or greater in volume, the method requires a more amount of source material and a longer time for product finishing. Because of cracking and warpage during sintering, the yield of overall manufacture is substantially reduced, resulting in an increased cost. This is a problem in the manufacture of ceramic thin plates.
For the related technology, reference should be made to patents including JP-A 10-204655, JP-A 6-33215, JP-A 2004-346374, and JP-B 6-55477.